Minor TextPipeline cleanup

[rparrett]

Objective

Both set_metrics and set_size can trigger text re-layout and re-shaping, if the values provided are different form what is already in the Buffer.

Solution

Combine the set_metrics and set_size calls.

This might be a small optimization in some situations, maybe when both font size and text bounds change in the same frame, or when spawning new text.

I did measure a ~500 microsecond improvement in text_system for many_buttons --respawn, but that may have just been noise.